This project is designed to delineate the neural substrate of cocaine reinforcement. Brain stimulation reward mapping will be used to determine anatomically-defined circuit elements and pharmacological challenge of intravenous cocaine self-administration will be used to determine neurochemically-defined elements. Pharmacological interactions of various drugs of abuse with brain stimulation reward will be used to determine the degree of overlap between the substrates of cocaine reinforcement and the substrates of other drug reinforcers.